The overall objective of this renewal application remains to discover novel chemopreventive agents derived from the natural products. This project will continue to utilize mammary gland organ culture and in vivo carcinogenesis models (skin and mammary) to evaluate biological effectiveness of potential chemopreventive agents identified in the initial screen. As indicated in the theme of this program, extracts or fractions considered as active leads will be first evaluated for its chemopreventive activity against 7,12, dimethylbenz(a)anthracene (DMBA) induced mammary lesions in organ cultures. If the exact shows dramatic activity in the culture system, it will be evaluated against two stage skin carcinogenesis model. Some extracts or isolated fractions will be further characterized and again their activity will be assessed. The newly identified agent which is considered active is again evaluated against mammary lesion formation. The active compound is then synthesized and carcinogenesis studies will be initiated. Brassinin and the extract of Mundulea sericea (P00053) were selected for the carcinogenesis experiments based on the results from the in vitro assays and organ culture experiments (this project). These studies have shown excellent inhibition against skin carcinogenesis. In addition we propose to conduct studies to evaluate activity of newly identified chemopreventive agent for its activity either as an anti-initiator or as an anti-promoter in organ cultures. This will allow us to design in vivo studies to confirm such stage specific effects and to understand the mechanism of action of these agents. A variety of other carcinogenesis models have been established in our laboratory for assessing chemopreventive potential at other target organs, and they will be used as required. In summary, this project will serve to provide a definite biological end point for newly identified potential chemopreventive agents in this program project.